1. Field of the Invention:
The present invention relates to an amine catalyst for producing a polyurethane or a polyisocyanurate, and a process for producing a flexible polyurethane foam employing the amine catalyst. More specifically, the present invention relates to a novel catalyst for producing a flexible polyurethane which has high activity for forming polyurethane or polyisocyanurate, giving less odor, giving high fire retardance, and having excellent curability, and also relates to a process for producing a flexible polyurethane foam by use, as a catalyst, of a quaternary ammonium carbonate which has high activity for polyurethane formation, having less odor, and being less corrosive.
2. Description of the Related Art:
Polyurethane products and polyisocyanurate products are widely used for furniture, automobile interior materials, insulating materials, and so forth. In recent years, the production of these products are required to be improved in productivity, moldability, physical properties, and so forth, and not to cause environmental pollution. Therefore, the catalyst is sought for to achieve high catalytic activity and high functionality.
For example, for improvement of productivity and moldability, a catalyst is demanded which is capable of curing at a high curing rate. For improvement of physical properties, a catalyst is demanded which is effective in improvement of fire retardance of an insulating material as a building material. For environmental protection, an amine catalyst or a blowing agent is demanded which has less odor, and the catalyst should be suitable for the formulation for flon consumption reduction.
A catalyst for formation of polyisocyanurate (trimerization) is exemplified by metal type catalysts such as alkali metal carboxylates, metal alcoholates, metal phenolates, metal hydroxides; tertiary amines; tertiary phosphines; and phosphorus onium salts. Alkali metal carboxylate salts such as potassium acetate, and potassium 2-ethylhexanoate are used owing to high activity of promoting isocyanurate reaction (isocyanurate activity) and effectiveness of improving fire retardance of a rigid foam as a building material. Quaternary ammonium salts of tetraalkylmonoamine type such as quaternary hydroxyalkyltrimethylammonium 2-ethylhexanoate (disclosed in JP-A-52-17484) are used owing to high isocyanurate activity. Furthermore, a method of employing a quaternary ammonium organic acid salt is disclosed in JP-A-9-124760.
Flexible polyurethane foams are widely used for furniture, automobile interior materials, bedding materials, cushion materials, and so forth. In recent years, the production of these polyurethane products are required to be improved in productivity, moldability, physical properties, and so forth, and not to cause environmental pollution. Therefore, the catalyst is sought to achieve high catalytic activity and high functionality.
For example, for improvement of productivity and moldability, a catalyst is demanded which is capable of delaying. For improvement of physical properties, a catalyst is demanded which is effective in improvement of air permeability. For environmental protection, an amine catalyst or a blowing agent is demanded which has less odor, and the catalyst should be suitable for the formulation for flon consumption reduction.
In production of polyurethane foams, the organic carboxylates of a tertiary amine disclosed in JP-A-60-58418 are known to be useful as delayed action catalysts. The delayed action catalyst, which has a low initial activity, is capable of delaying the time of initiation of the foaming reaction-after mixing of the source materials, the polyol and the organic isocyanate. Therefore, the handling of the liquid mixture and the flowability of the mixture, and other properties are improved. For example, the source material liquid can be filled sufficiently to the corner of a large mold. This type of catalyst exhibits the catalyst activity by thermally dissociating the tertiary amine compound when the foaming reaction has proceeded to cause rise of the reaction temperature. Consequently, the catalyst activity is greatly increased to allow the produced foam to distribute throughout a complicated mold without defect formation, and thereby the curing is accelerated to shorten the mold-release time of the produced foam and improves the productivity.
However, conventional catalysts for rigid isocyanurate foam production have various disadvantages. For example, conventionally used alkali metal carboxylates and tetraalkylmonoamine type quaternary ammonium salts, although they have relatively high isocyanuration activity, delay the initial reaction remarkably but accelerate the isocyanuration at the later stage of foaming to result in rapid rise of-the foaming profile, impair the flowability and broaden the density distribution disadvantageously. Further, the conventional tetraalkylmonoamine type quaternary ammonium salts evolve low-volatile amine by decomposition of the quaternary ammonium salt during the foam formation to aggravate working environment. Further more, when a tertiary amine is combinedly used for accelerating the initial reaction and improving the foam flowability, although it improves the flowability, the tertiary amine generates strong odor, renders the foam more friable, and lowers fire retardance because the isocyanuration is retarded, disadvantageously.
On the other hand, the for polyurethane production catalyst having been employed because of their delayed action has various disadvantages. For example, organic carboxylic acid salts of a tertiary amine are strongly corrosive because of its lower pH, and tend to corrode materials such as a urethane foaming machine to lower the productivity, disadvantageously. This disadvantage can be overcome by decreasing the amount of the organic carboxylic acid to raise the pH, but this offsets the desired delaying effect. In one method, a suitable tertiary amine is mixed to the tertiary amine carboxylate to solve the problem, but the corrosion cannot be completely prevented because of the essential use of an organic carboxylic acid.